Heterocyclic rings are present as fundamental components in the skeletons of more than half of the biologically active compounds produced by nature. With this in mind, there have been great efforts to discover and optimise new reactions that will facilitate the construction of heterocycles, especially when the methodology leads to a new type of N-based heterocycle. A facile route to a new family of heterocycles opens the possibility of finding new types of biologically active units that can be used in the generation of libraries of compounds, or for use in the development of new methodologies to be applied in organic synthesis.
Yamazaki et al (J. Heterocyclic Chem., 16: 517-525, 1979) discloses the synthesis of Dihydro-Benzo[f]Imidazo[1,2-a]quinoline in three steps with an overall yield of 40%. The compounds produced also have the disadvantage that they are not functionalised.
Koyama et al (Chem. Pharm. Bull., 23(9):2015-2018, 1975) discloses the synthesis of dihydro-imidazo-benzo [h] quinazolinium in three steps with one example of substitution at one position on the molecule.
Preston et al (J. Med. Chem., 471-480, 1964) discloses the synthesis of dihydro-imidazo-quinolinium in three steps at very low yield (10%).
Osbond (J. Chem. Soc., 1853-1856, 1950) also discloses the synthesis of dihydro-imidazo-quinolinium in four steps.
U.S. Pat. Nos. 5,401,847 and 5,783,687 (Glazer et al) relate to fluorescent compounds that are not based on substituted phenanthridinium derivatives but which have the property of binding DNA.
EP 1 223 226 A (Tosho Corporation) discloses a family of molecules in which a phenanthridinium compound is linked to two further heterocyclic ring systems, see Formula 1. The phenanthridinium portion of the compound consists of a three ring heterocycle with a phenyl group in the alpha position relative to the heterocyclic nitrogen.
WO 95/01341 (Abbott Laboratories) discloses phenanthridinium compounds that consist of three ring heterocycle with a phenyl group in the alpha position relative to the heterocyclic nitrogen and which have two amine substituents on the first and third rings. These compounds are disclosed as DNA intercalators.
Chemical abstract numbers 1977:121139 (Roques et al, 1976) relates to a phenanthridinium compounds which is a three ring heterocycle with a phenyl group in the alpha position relative to the heterocyclic nitrogen.